Direction finder for radiowaves



2 Sheets-Sheet 2 .7; Csim 9+1) MQWSQ I) M (sine-I) ,7)! (my 6- 7) A.BAILEY DIRECTION FINDER FOR RADIOWAVES Filed April 25, 1928 Jan. 5,1932.

,INVEN'II'OR I vZfimzle -BY ATTORNEY Patented Jan. 5, 1932 AUSTINBAILEY, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE ANDTELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

DIRECTION FINDER FOR RADIOWAVES Application filed April 25, 1928 SerialNo. 272,702.

This invention relates to theart of radio communication, and morespecifically to radio receiving apparatus for determining both themagnitude and absolute direction of propagation of radio waves.

The invention utilizes three separate coaxial antennae comprising avertical antenna and two identical loop antennae the planes of which areset at right angles. Currents from the three antennae are combined insuch manner that when impressed upon two pairs of deflecting plates of acathode ray oscillograph, which pairs of plates are set at right angles,a deflection of the electron stream on the screen is obtained which indicates both the magnitude and the absolute direction of propagation ofthe radio wave train impinging upon the antenna system.

.The receiving system for accomplishing the above results is bestexplained by reference to the drawings of which Figure 1 shows inperspective and in schematic form the arrangement of the antenna system;Fig. 2 shows a plan view of the antenna system when viewed from above,together with certain mathematical relations necessary for explainingthe theory of operation of the system; Fig. 3 shows schematically theelectrical circuits to which the antennae are connected, together withcertain mathematical relations to be explained concerning the theory ofcircuit operation; Fig. 4 shows graphically the manner in which thecurrents in the different output circuits'of Fig. 3 vary with thedirection of propagation of the impinging radio Wave train; and Figs. 5to 8 show the variation with time of the currents in the output circuitsof Fig. 3 for difierent shown.

assumed conditions of current rectification.

Referring more-specifically toFig. 1, loop antennae 1-2 and 3-4 arearranged coaxially with their planes at right angles to each other andperpendicular to the ground, as Coaxially with the loop'antennae is thevertical antenna 5. The three antennae are electrically separate, asshown.

Referring'now tov the plan view of the antenna system'shown in Fig. '2,assume a radio wave train to be traveling in the .direction XY. Takingthe axis 0 of the antenna system as an origin of coordinates, and thedirection X to Y as positive, a single frequency wave train impingingupon the antenna system is given by the equation E =E Sill w (t%) (1)21F frequency and t= tlme.

I From Equation (1), the Volta e induced in the vertical wires 1(Fig. 1) 0 loop 1-2 is given by A E =K E sin to (H SZ 9) 2 where K is aconstant depending upon the number and length of the vertical wires 1;

0 is the angle between-the plane of the loop and the direction of wavepropagation h is the distance between the vertical leads of the loop 12.

In a similar manner, the voltage induced in the vertical wires 2 of loop12 is given by Ezv=K1E0 sin to (t 2 p The resultant voltage E induced inthe loop 12 is given by the difference of equations (2) and (3), namelyQ h-cosl) a SIMO- (4) The right side of Equation (4) may be'expressedmore simply as w"=2K, sin l:|-cos wt (5 and since wk cos 0 is'small incomparison with 'tenna. circuit 9.

24;, the sine of the bracketed member may be replaced by the angle,giving For a given frequency, this becomes where K is a constant. Bysimilar processes, the voltage E in loop 3-4 is E ==K -E cosB-coswtwhere K is a constant depending on the proportions of the antennacircuit. Comparing Equations (7), (8) and (9) ,it will be seen that thevoltages induced in the vertical antenna lag in phase 90 behind thecorre sponding voltages induced in the loop antennae. To obtain the bestresults in regard to directional effects by combining the voltageinducedin a loop antenna with that of the vertical antenna, the voltages shouldbe combined in like time phase relation. These phase relationships arecared for by the circuit of Fig. 3 in a manner now to be explained.

, Assume the three antennae voltages of Fig. 1 to be applied to thecircuit of Fig. 3, as indicated. The currents are amplified inamplifiers 1, are combined with a heterodyne frequency supplied fromoscillator 2 and are demodulated and amplified in circuits 3, 4 and 5.The output current from the beating oscillator 2 is fed through theresistance 7 and capacity 6connected in series. The voltage drop acrossthe condenser 6 is applied to the loop 'antennae circuits 8 and 10,while that across ag lied to the vertical anmce the voltage drop acrassthecondenser is 90? out of phase with that across the resistance, theheterodyne current applied to circuits 8 to 10, inclusive, owing to themanner of connecting the beating oscillator to such circuits, isexpressed mathematically, as indicated on Fig. 3. The total currentinput to each modulator device 3 to 5, inclusive, is mathematicallyexpressed by the expressions36 to 38 inclusive, of Fig.

the resistance 7 is 3. The output from demodulator 3 will con:

tain, among other things, the product term E7 I in which' the bracketedmember is equal tothe sum and difierence of the two/frequencies.Be-writing Equation (10) in this form, keep ing only the differenceterm, gives By similar treatment, the output from demodulator 5 is Theoutput from demodulator 4 contains the product term E =K -E -0- 2sinwt'cos t 13 which re-written, retaining only the difference term,gives E; =K,-E 0- Sin ea 14 If the amplifier unit associated withdemodulator'4 is properly adjusted with respect to units 3 and 5, thefollowing relation can be obtained thus giving the output currents shownat 11 to 13, inclusive, of Fig. 3 in which 'change the phaserelationship of they current induced in the vertical antenna withrespect to that induced in the loopantennae. lhe outputs from thedemodulator circuits 3 to 5, inclusive, are fed into the transformercircuits 18 and 19 in the manner shown on Fig. 3. .Owing to the mannerin which current from the vertical antenna is fed into the transformercircuit 18, demodulated current 11 from loop. antenna 1-2.is combined intransformer 14 in like time phase relationship with demodulated current12 in the vertical antenna. 11 is combined in phase opposition withcurrent 12. In transformer 16. current 12 is combined in like phaserelation with current 13, and in transformer 17 current 12 is combinedin phase opposition to current 13. The resulting currents flowing intorectifier circuits 24 to 27, inclusive, are given by currents 20 to 23,respectively. I

At this point it is well to consider the manner in which currents 20 to23, inclusive, vary with the direction of propagation of the wave trainimpinging upon the antenna system. Fig. 4 shows a plot of currents 20 to23, inclusive, at the instant when w t=1r/2, plotted against thedirectional angle 0 as a variable. The current designations 20 to 23,inclusive, are the same in Fig. 4 as in Fig. 3.

In transformer 15 current its The graph of Fig. 4 shows four cardiodsarranged successively at right angles. As m t varies from zero to 2%,each cardiod increases from a point toa maximum value of 2M theimpinging radio wave train is propagated but there would be an ambiguityof 180?. For example, it would not be known whether the Wave weretraveling from east to west 1 or from west to east, say. If, however,the

. rent in each output circuit will vary with time currents 20 to 23 3)are passed through rectifying devices 24 to 27, inclusive, such that therectified direct current in the output of each such circuit isproportional at each instant to the input alternating current, theserectified currents may be combined to indicate the absolute direction ofpropagation as well as the magnitude of the radio wave train. This isdue to the fact, referring for a moment to Fig. 4, that afterrectification the cardiods will not reverse in direction but will merelyincrease from zero to a maximum value, returning again to zero.

Referring to Fig. 3, the rectified currents 28 to 31 flow through equalresistances 39 to 42, inclusive, the output circuits of the rectifiers24 to 27. inclusive, being arranged so that current 28 is poled oppositeto current 29 and current 30 opposite to 31. The potential drop due tocurrents 28-and 29 flowing through resistances 39 and 40. respectively,is impressed upon a pair of deflector plates 34 of a cathode rayoscillograph 32-, in themanner shown. With this connection, the

voltage impressed across the deflector plates is proportional to thedifference of the currents 28 and 29 In a similar manner. the potentialdrop due to currents 30 and 31 flowing through resistances 41 and 42,respectively, is impressed upon a pair of deflector plates 33 associatedwith the oscillograph 32, which deflector plates 33 are placed at rightangles to deflector plates 34, as shown.

Assuming full wave rectification in rectifiers 24 to '27 inclusive,.therectified curin manner shown in Fig. 5. Referring now to Fig. 4, avoltage will be impressed upon the deflector plates 34 of theoscillograph 32 which is proportional to rectified current 21 subtractedfrom current 20. If D 4) indicates the direction of propagation of thewave train, the voltage impressed upon deflector plates 34 will beproportionalto Correspondingly, the voltage impressed to current 23subtracted from current 22, or

referring to Fig. 4, the voltage is proportional to 'amaeocai+ag=alc.

Since the voltage impressed upon plates 34 acts upon-the electron streamof the oscilliograph'at right. angles to the voltage im-' pressed uponplates 33, the electron stream will be deflected along a line determinedby.

the resultant of these two voltages added 7 vectorially. Referring toFig. 4, the resultant voltage impressed upon the electron stream isproportional to up, which is obtained by adding 070?]?(5 at right anglesto ad. Since the rectified currents 28 to 31, in-

clusive, as explained above, fluctuate between zero and a maximum valueproportional to the input alternating currents 20 to 23, inclusive, theelectron stream will periodically trace out a path on the screen 36 ofthe oscillograph 32 from the center of the tube to a maximum value andback again along a line making an angle 0 with the horizontal, the

length of the path thus traced out being proportional to the magnitudeof the voltage impressed upon the antenna system by the impinging radiowave train.

- It will thus be seen from the explanation given above that theinvention covers a circuit arrangement furnishing a method of de- Ktermining both the magnitude and direction of propagation of a radiowave train impinging upon the antenna'system.

It was shown above that for full wave rectification the currents 28 to31, inclusive, fluctuated with time in the manner shown' in Fig. 5. Forhalf wave rectification the currents would fluctuate with time, as-shownbycurve 1 of Fig. 6. This same result could be obtained by combiningfull wave rectification with non-rectified current of the same peakvalue, as shown, by adding curve 2 to curve 3 of Fig. 6. For observingupon sustained oscillations'of constant amplitude it might be advisablein some instances to insert low pass filters in the output circuits ofthe rectifiers 24 to 27, inclusive, of Fig. 3, the purpose of whichwould be to smooth out the fluctuating rectified currents flowingthrough resistances 39 to 42, inclusive, into steady direct currents, asshown in Fig. 7. The resultant filtered direct current throughresistances 28 to 31, in-

clusive, would impress constant potentials point and the origin wouldmake an angle- 0 with the horizontal, indicating the direction ofpropagation of said wave train, the direction from which the waveimpinged being indicated by the quadrant of the circle in which i thepoint was located. Fig. 8 shows the manner inwhich the volta e impressedacross the deflector plates varies with time when filtered rectifiedcurrent is combined with non-rectifiedalternating current of the samemaximum value.

What is claimed is:

1. In a circuit for determining the magnitude and direction ofpropagation of radio waves, the combination of three coaxially alignedantennae comprising two identical loop antennae, the planes of which areset at right angles to each other, and a vertical antenna, means forseparately amplifying and demodulating the currents induced in the threeantennae circuits in' such manner that the demodulated currents are inlike time phase relation, means for combining in a first electricalcircuit demodulated current from,

.in phase opposition, rectifying means individual to said fourelectrical circuits adapted to impress -.upon identical resistancesindividual to the outputs of each of said rectifying circuits,fluctuating direct voltages proportional to the alternating voltagesimpressed upon said rectifiers, a cathode ray oscillograph havingassociated therewith two pairs of deflecting plates set. at right anglesto each other, means for impressing upon one pair of deflectin plates avoltage proportional to the di erence of the two rectified currentsfirst mentioned, and means for impressing upon the second pair of saiddeflectmg plates a voltage proportional to the difference of the tworectified currents last mentioned. I

2. In a radio receiving circuit for determining the magnitude anddirection of propagation of radio waves, the combination of threecoaxially aligned antennae comprising a vertical antenna and twoidentical loop antennae the planes of which are set at right angles,electrical circuits iIldlVidl13.l tO said antenna, amplifiers in each ofsaid electrical circuits, a source of locally generated oscillatingcurrent, means for applying said locally generated current directly toeach of the electrical circuits associated with the loop antenna, meansfor applying the locally generated oscillations through a phase shiftingdevice to the vertical antenna circuit, said phase shifting device beingadapted to cause said currents, applied to the vertical antenna, todiffer in phase by 90 degrees ascompared to that applied to the loopantenna circuits, demodulating and amplifying circuits individual to thethree antenna circuits, a system of interconnected transformerassociated with the output circuits of the amplifiers last mentioned,said transformer circuits being adapted to combine in a first electricalcircuit demodulated current from the vertical antenna circuit in liketime phase with similar current from a given loop antenna circuit, saidtransformer circuit being further adapted to simultaneously combine in asecond electrical circuit demodulated current from the vertical antennacircuit with similar current from said loop antenna circuit but in phaseopposition thereto, said transformer circuit being further a'daptedtosimilarly combine in a third and a fourth electrical circuit,respectively, demodulated cur-' rent from the vertical antenna circuitwith similar current from the second loop antenna circuit in like timephase relation and in phase opposition thereto, respectively, rectifyingcircuits individual to each of said four electrical circuits adapted tofurnish in the output circuits fluctuating direct currents proportionalto the alternating current impressed upon the inputs, a cathode rayoscillograph having associated therewith two is set at right angles tothe other, means for impressing upon one pair of said deflecting platesa voltage proportional to the difference of the two rectified currentsobtained from the vertical and a given loop antenna, and means forimpressing upon the second pair of deflecting plates a voltageproportional to the difference of the two rectified currents obtainedfrom the vertical and the second loop antenna circuits.

3. In a radio receiving circuit for determining the magnitude anddirection of propagation, of radio waves, the combination of threecoaxially aligned antennae comprising a vertical antenna and twoidentical loop antennae, the planes of which are set at right angles,electrical circuits individual to said antenna, amplifiers in each ofsaid electrical circuits, a source of locally generated oscillatingcurrent, means for applying said 10- cally generated current directly toeach of the electrical circuits associated with the loop antenna, meansfor applying the; locally pairs of deflecting plates, one pair of whichpared to that applied to the loop antenna circuits, demodulating andamplifying circuits individual to the three antenna circuits, a systemof interconnected transformers astrical circuit demodulated current fromthe vertical antenna circuit in like time phase with similar currentfrom a given loop antenna circuit, said transformer circuit beingfurther adapted to simultaneously combine in a second electrical circuitdemodulated current from the vertical antenna circuit in like time phasewith similar current from a given loop antenna circuit, said transformercircuit being further adapted to simultaneously combine in a secondelectrical circuit demodulated current from the vertical antenna circuitwith similar current from said lo'op antenna circuit but in phaseopposition thereto, said transformerv circuit being further adapted tosimilarly combine in a third and a fourth electrical circuit demodulatedcurrent from the vertical antenna circuit with similar current from thesecond loop antenna circuit in like time phase relation and in phaseopposition thereto, respectively, rectifying circuits individual to eachof said four electrical circuits adapted to-furnish in the outputcircuits fluctuating direct currents proportional to the alternating current impressed uponthe inputs, low pass filters inserted in the outputcircuits of sa1d rectifiers and individual thereto, said low passfilters being adapted to transform the fluctuating direct current to asteady direct current, a cathode ray oscillograph having associatedtherewith two pairs of deflecting plates, one pair of which is set atright angles to the other, means for impressing upon one pair of saiddeflecting plates a voltage proportional to the difference of the tworectified currents obtained from the vertical and a given loop antenna,and means for impressing upon the second pair of deflecting plates avoltage'proportional to the difference of the two rectified currentsobtained from the vertical and the second loop antenna circuits.

4. The method for determining the mag-- nitude and direction ofpropagation of radio waves, which comprises, detecting componentsthereof which vary in accordance with said direction of propagation,detecting other components which are independent of said direction,combining said dependent with said independent components and rectifyingthe same, deflecting an electronic stream in accordance with saidrectified com ponents to give an indication of the magnicomponents whichare dependent thereupon, combining said dependent with said independentcomponents and rectifying the same, deflecting an electronic stream inaccordance with said rectified components to give an indication of themagnitude of said waves and the direction of the source thereof.

6. The method for determining the mag nitude and absolute direction ofpropagation of a radio wave train, which comprises, de-

tecting a first component thereof which varies in a certain manner inaccordance with said d1rect1on of propagation, detecting a secondcomponent thereof which varies .in a differ-- ent manner in accordancewith said direction, detecting a third com onent thereof which isindependent of said irection, independently combining said first andthird and said second and third components, rectifying saidcombinations, deflecting an electronic stream in accordance with saidrectified combinations, and causing said-deflected stream to indicatethe magnitude and absolute propagation direction of said wave train.

7. The method for determining the magnitude and absolute propagationdirection of a I radio wave train, which comprises, detecting a firstcomponent thereof which varies in a certain manner in accordance withthe direction of said propagation, detecting a second component whichvaries in a different manner in accordance with said direction, detectmga third component which is independent of said direction, combining saidfirst and third components in like phase relation and in phaseopposition, similarly combining said second'and third components,rectifying said combinations, deflecting an electronic beam inaccordance with the dlfl'erence of said first two rectified combinationsand atan angle thereto deflecting 'said beam in accordance with thedifference of said last two rectified combinations, and causing saiddeflected beam to indicate the magnitude and absolute direction ofpropagation of said wave train.

8. The method for determining the magnitude and absolute direction ofpropagation of a radio wave train, which comprises, indedifference ofsaid first two rectified combina-' tions, and at right angles theretodeflecting said beam in accordance with the difference of said last tworectified combinations, and causing said deflected beam to indicate themagnitude-of said wave train and also the direction from whence itissues.

9. The method for determining the magnitude and absolute direction ofpropagation of a radio wave train, which comprises, independentlydetecting components of said wave train proportional-to the sine andalso to the cosine of the angle which the propagation direction makeswith an arbitrarily chosen direction, and also a component independentof said propagation direction, independently combining said sinecomponent in like'phase relation with said independent component andalso in phase opposition thereto, similarly combining said cosinecomponent with said independent component, separately rectifying thefour combinations thus obtained, deflecting a concentrated electronicbeam with a voltage proportional to the difl'erence of said tworectified currents containing said sine components, and at right anglesthereto deflecting said beam with a voltage proportional to thedifli'erence of the two rectified currents containing said cosinecomponents and caus ing said deflected beam to visibly indicate themagnitude of said wave train as well as the direction from whence'itissues.

10. Means for determining the magnitude and absolute direction ofpropagation of radio waves, comprising in combination, a verticalantenna and coaxial therewith two loop antennae set at an angle to eachother, means for combining in like phase relation and also in phaseopposition, currents from said vertical and a first loop antenna, meansfor similarly combining currents from said vertical and said second loopantenna, means for rectifying said current combinations, a cathodev rayoscillograph having one pair of deflecting plates set at an angle to thesecond pair, means for applying to said first pair of plates a voltageproportional to the difference of said two rectified currents firstmentioned, and means for applying to said second pair of plates avoltage proportional to the difference of said two rectified currentslast mentioned, where-' by said oscillograph indicates both the magni;tude and the absolute direction ofpropagation of said wave train.

11. Means for determining the magnitude and absolute direction .ofpropagation of" radlo waves, whlch comprises in combination,

a vertical antenna and coaxial therewith two J loop antennae the planesof which are set at right angles to each other, means for combining inlike phase relation and also in phase opposition currents from saidvertical and a first loop antenna, means 'for similarly combiningcurrents from said vertical and said second loop antenna, means forrectifying said. combined currents, a cathode ray oscillograph having afirst pair of deflectin plates set at right angles to a second Sui] air,means for applying to said first pair of p ates a voltage proportionalto the diflerence of said two rectified currents first mentioned, andsimilar means for applying to said second pair of plates a voltage proortional to the difi'erence of said two recti ed currents lastmentioned.

12. Means for-determining the magnitude and absolute direction ofpropagation of radio waves, which comprisesin combination, a verticalantenna and coaxial therewith a first loop antenna set at right anglesto a second identical loop antenna, amplifying and heterodyne detectingmeans individual to said antennae for adjusting the magnitudes of thedetected currents therein to the same value and also for adjusting saidcurrents in like phase relation,lmeans for combining in like phaserelation and also in base opposition detected currents from-saidvertical and a first loop antenna, means for similarly combiningcurrents from said vertical and said second loop antenna, means forindependently rectifying said current combinations, a cathode rayoscillograph having one pair of deflecting plates set at right angles toa secondpair, means for applying to said first air of plates a voltageproportional to the di erence of said two rectified current combinationsfirst mentioned, and means for applying to'said second pair of plates avoltage proportional to the difference of said two rectified currentcombinations lastmentioned, whereby said oscillograph indicates both themagnitude and the absolute direction of propagation of said wave train.

13. The methodeof determining the magnitude and absolute direction ofpropagation of radio waves, which consists in detecting componentsthereof, combining one of 'said componcnts with a second one of said comonents and a third one of said components with said second one,rectifying said combinations, deflecting an electronic beam inaccordance with the difference of said first two rectified combinations,deflecting said beam at an angle thereto in accordance with thedifl'erenceof said last two rectified combinations and causing saiddeflected beam to indicate the magnitude and absolute direction ofpropagation of said waves.

14. Means for determining the magnitude and absolute direction ofpropagation of radio waves comprising in combination a vertical antenna,two loop antennae setat an ing said rectified current combinations tosaid latter means to deflect said beam and cause it to indicate themagnitude and absolute direction of propagation of said waves.

In testimony whereof, I have signed my name to this specification this23rd day of April, 1928.

' AUSTIN BAILEY.

